Mixer unit for a plurality of incoming signals



w. L. LARSON 2,783,397

MIXER UNIT FOR A PLURALITY OF INCOMING SIGNALS I 2 Sheets-Sheet 1 Feb. 26, 1957 Filed July 27, 1953 Feb. 26, 1957 w. L. LARSON MIXER UNIT FOR A PLURALITY OF INCOMING SIGNALS Filed July 27, 1953 2 Sheets-Sheet 2 W (a f g x 1a 6 Z d5 57 W33. 0 f a a w ||l llllll a 3 w 3 W 2,783,397 MIXER UNIT FOR A PLURALITY F INCOMING SIGNALS Wiifred lL. Larson, Chicago, 111., assignor to Switchcraft, Inc., Chicago, 111., a corporation of Illinois Application July 27, 1953, Serial No. 370,398 4 Claims. (Cl. 307-156) This invention relates generally to devices for controlling the attenuation of a plurality of incoming signals which are combined at a. single output terminal.

The device according to the present invention is especially adapted for use in recording a radio or other audio program upon tape or other record medium for subsequent playback. Disc jockey shows, for example, are recorded upon a magnetic tape at a convenient time and subsequently broadcast. The recording equipment commonly employed oftentimes has only a single input terminal, and the incoming signals, one from a disc recording, and the other from the announcer, are desirably controlled in their attenuation for making announcements or for other reasons.

Heretofore mixer panels have been provided for attenuating the signals desirably, but such devices have always required the use of two hands for fading in and out of the signals as desired.

With the foregoing considerations in mind, it is a principal object of this invention to provide a device for mixing and controlling the attenuation of a plurality of incoming signals.

Another object is to provide such a mixing device which can be detachably mounted at the input terminal of a recording device or the like, and which can be controlled readily by the manipulations of one hand only of the operator, thereby leaving the other hand free for other operations.

' Other objects and important features of the invention will be apparent from a study of the following specification taken with the drawings which together describe and illustrate some preferred embodiments of the invention and what are now considered to be the best mode of practicing the principles thereof. Other embodiments of the invention may be suggested to those having the benefit of the teachings herein, and the scope of the invention is therefore intended to include such other embodiments especially as they fall within the purview of the subjoined claims.

in the drawings:

Fig. 1 is a perspective view substantially at full size of a mixer unit constructed according to the present invention;

Fig. 2 is a horizontal sectional view taken along the plane 2-2 indicated in Fig. l and looking in the direction of the arrows, certain parts being shown in plan view;

Fig. 3 is an end view looking in the direction of the arrows 73-3 of Fig. 2;

Fig. 4 is a longitudinal section taken along the line 4-4 of Fig. 3 looking in the direction of the arrows;

Fig. 5 is a transverse section taken along the line 55 of Fig. 2, certain parts being shown in elevation;

Fig. 6 is a schematic diagram showing the manner in which the parts are electrically connected .within the mixer unit; and

Fig. 7 is an alternate form of mixer unit according to the present invention.

Referring now to the drawings the improved mixer unit according to the present invention is designated generally by the reference numeral 10 and includes an essentially parallelepiped-shaped housing having upper and lower walls 11 and 12, side walls 13 and 14 and an end wall 16. The housing 15 is completed by an end closure 17 including a flange 18 which is crimped round the edges nited States Patent 0 "ice of the upper and lower walls 11 and 12 and the opposed side walls 13 and 14. In the form shown herein the housing 15 maybe made from a pair of stampings in a manner well known in the art.

The end wall 16 is provided with a central aperture 19 and forms a support for a plug 21 having a pair of flanges 22 and 23 which are crimped upon the end wall 16 at the aperture 19. The plug 21 has a hollow shank 24 having coaxial therewith a plug tip 26 insulated from the hollow shank 24 by an insulating washer 27 and an insulating sleeve 28. A soldering lug 29 is threaded to the plug tip 26 at the end thereof extending within the housing 15 and is insulated from the hollow shank 24 by means of an insulating washer 31.

The structure thus far described affords an output terminal for a pair of input signals which may be desirably attenuated by the device according to the present invention as will now be described.

The end closure 17 supports a pair of spaced input jacks referred to generally by the reference numerals 3t) and 39a. Reference will be made to the input jack 30 and all description thereto pertains to the input jack 30:: as well.

The jack 3!} includes a threaded sleeve 32 having a flange 33 and a crimping flange 34 holding therebetween an insulating sleeved washer 36, a grommet 37 continuous with a jack arm 38 with a locking crimp 39 near the end thereof, an insulating washer 41 and a spacer ring 42.

The construction of such a jack is well known in the art and need not be described in further detail. Suflice it to say, however, the jack 30 is of a construction adapted to cooperate with a plug of construction similar to the plug 21 supported in the end wall 16. The jacks 3G and 30a are thus arranged to cooperate with a pair of plugs, not shown, each connected to a separate source of audio signals or the like, such as those emanating from a phonograph pickup and amplifier and an announcers microphone or the like.

The two incoming signals at the jacks 30 and 30a are adapted to be attenuated as desired, and to this end the top wall 11 of the housing supports by means of cap screws 43, 43, a chassis 44 having a pair of downward extending spaced legs 46 and 46a. The legs 46 and 46a afford respectively a support for a variable resistance element indicated generally by the reference numerals 47 and 47a. The description obtaining for variable resistance element 47 will suffice also for variable resistance element 47a. Variable resistance element 47 is supported upon spaced studs and retaining nuts 48 which hold it to the downward extending leg 46. Each variable resistance element include an essentially cylindrical shaped rotating operator 49 having elements thereof extending through rectangular shaped apertures 51 in the upper wall 11 of the housing 15. In order to support the cylindrical shaped operator 49 of the variable resistance element 47, the chassis 44 has adjacent the leg 46 a generally rectangular shaped aperture 52 which is in alignment with the aperture 51 in the upper wall 11. The other variable resistance element 47a is mounted on the outside of the downward extending leg 46a and no aperture corresponding to aperture 52 for the other variable resistance element is needed, therefore.

The variable resistance elements 47 and 4701 may be of the type employed in hearing aids and are of high quality to minimize any distortion or the input signais at the jacks 30 and 3001. Referring now to Fig. 6, each variable resistance element 47 includes a resistance '53 of the order of one megohm, and each is connected by a lead 54 to the terminal 29 of the plug 26. As is conventional in such variable resistance elements each includes a Wiper arm 56 which is connected in series with a fixed isolating resistance 57 of the order of 120,009 ohms to a lead 563 soldered to a lug 59 on the grommet 37 of the jack 30.

The isolating resistors 57 and 57a in series with each input signal at the jacks 30 and 39a and their respective variable resistance elements minimize any impedance mismatch or any resulting distortion in various positions of the wiper arms 56 on the resistances 53.

It Will be seen from Fig. 6 that the housing forms a ground to which is connected one side of each or" the jacks and 30a and the shank 24 of the output plug 21. The other end of each variable resistance element 53 is also connected by means of a lead 61 to ground.

Referring now to Fig. 7 of the drawings there is shown another embodiment of the invention difiering only from the embodiment just described by having the end closure 17 afiord a support for a pair of chassis mounted male connectors 62 and 62a. The end wall 16 instead of having the plug as shown in the previous figures afiords the support for a female receptacle indicated by the reference numeral 63. Any combination of connectors may be furnished, as desired, of jacks, plugs, chassis mounted male connectors and female receptacles as desired, and all such other forms are intended to be embraced Within the present invention.

From the foregoing description it will be evident that the two operators 49 and 49a are in alignment respective ly with the input terminals 30 and 300 or the input terminals 62 and 62a shown in Fig. 7. In operation, the mixer unit 10 is of course supported at the input terminal on the panel of a tape recorder or similar device and the operator may attenuate the incoming signal at each incoming terminal 30 or 30a by manipulation of the operators 49 and 49a with the fingers of one hand only, thereby permitting the other hand to be used for other operations.

It will be apparent of course that the two cylindrical operators 49 and 49a may be used for fading out music and fading in the voice of an announcer or any other set of operations as desired.

While the invention has been described in terms of a number of embodiments which it has assumed in practice it is not intended that the scope of the invention be limited by the precise embodiments herein shown, other forms thereof being intended to be reserved especially as they fall within the scope of the claims herein appended.

I claim as my invention:

1. In apparatus of the class described for controlling the attenuation of a plurality of signals connected to a common output, a housing having a pair of spaced end walls, circuit completing means for an output signal, said circuit completing means being supported by one of said end Walls, at least a pair of circuit completing means supported on the other of said end walls, each of said last named circuit completing means being for an input signal, means supported Within and by said housing for supporting a pair of variable resistance elements being in aligtn ment with one of the last named circuit completing means on said other end wall, an aperture in said housing at each of said variable resistance elements and a rotating operator for each of said variable resistance elements, part of the element only of said rotating operators extending through said apertures whereby said operators may be manipulated by the fingers of one hand only if desired, each of said operators being related in position to a corresponding one of said last named circuit completing means whereby operation of each is related to the attenuation of the signal at the first named circuit completing means.

2. In apparatus of the clas described for controlling the attenuation of a plurality of signals connected to a common output, a housing having an end wall and a closure spaced from said end Wall, circuit completing means for an output signal, said circuit completing means being supported by said end wall, at least a pair of circuit completing means supported on said closure, each of said last named circuit completing means being for an input signal, means supported Within and by said housing for supporting a pair of variable resistance elements. each of said variable resistance elements being in alignment with one of the last named circuit completing means on said closure, an aperture in said housing at each of said variable resistance elements and a cylindrical shaped rotating operator for each of said variable resistance elements, part of the elements only of said cylindrical shaped rotating operators extending through said apertures Whereby said operators may be manipulated by the fingers of one hand only if desired, each of said operators being related in position to a corresponding one of said last named circuit completing means whereby operation of each is related to the attenuation of the signal at the first named circuit completing means.

3. In apparatus of the class described for controlling the attenuation of a plurality of signals connected to a common output, a housing having a pair of spaced end walls, circuit completing means for an output signal, said circuit completing means being supported by one of said end walls, at least a pair of circuit completing means supported on the other of said end walls, each of said last named circuit completing means being for an input signal, a chassis held within said housing and supported thereby, a pair of variable resistance elements supported on said chassis, each of said variable resistance elements being in alignment with one of the last named circuit completing means on said other end wall, an aperture in said housing at each of said variable resistance elements and a rotating operator for each of said variable resistance elements, part of the elements only of said rotating operators extending through said apertures whereby said operators may be manipulated by the fingers of one hand only if desired, each of said operators being related in position to a corresponding one of said last named circuit completing means whereby operation of each is related to the attenuation of the signal at the first named circuit completing means.

4. In apparatus of the class described for controlling the attenuation of a plurality of signals connected through said apparatus to a common output, a housing having an end wall and a closure spaced from said end wall, circuit completing means for an output signal, said circuit completing means being supported by said end wall, at least a pair of circuit completing means supported on said closure, each of said last named circuit completing means being for an input signal, a chassis held Within said housing and supported thereby, a pair of variable resistance elements supported on said chassis, each of said variable resistance elements being in alignment with one of the last named circuit completing means on said closure, an aperture in said housing at each of said variable resistance elements and a cylindrical shaped rotating operator for each of said variable resistance elements, part of the elements only of said cylindrical shaped rotating operators extending through said apertures whereby said operators may be manipulated by the fingers of one hand only if de sired, each of said operators being related in position to a corresponding one of said last named circuit completing means whereby operation of each is related to the attenuation of the signal at the first named circuit completing means.

References Cited in the file of this patent The Radiotron .Designer Handbook (third edition), by F. Langford Smith; pages 81 to .83. Distributed by RCA Manufacturing Company. 

